WESPs provide efficient emission controls for submicron particulates, heavy metals, acid mists, fumes, dioxins and furans. WESPs are specifically designed to handle process gas cleaning problems at low capital and operating costs. One form of WESP is described in WO 92/19380, the disclosure of which is incorporated herein by reference.
WESPs are adaptable to a wide variety of gas cleaning operations and are particularly effective at collecting sub-micron particles, regardless of the physical or chemical nature of the collected material. WESPs contrast with alternative collection methods, such as scrubbers, fabric filters and dry electrostatic precipitators, which are often sensitive to the composition of the collected material.
The WESP usually consists of a bundle of vertical discharge tubes, often of hexagonal shape, each tube having a high-voltage rigid rod-like (mast) electrode axially arranged therein. Gas enters the WESP, where it is evenly distributed across the tube bundle. Incoming particles are given a strong negative charge by a high density ionizing corona produced by the high voltage electrodes. As the gas flows through the vertical discharge tubes, the action of the electric field on the charged particles causes them to migrate to the grounded walls of the tubes where they accumulate. The self-washing action of a water film that falls down the inside of the tube removes the collected material to a discharge drain.